System of radio communication



E. F. W. ALEXANDERSON.

SYSTEM OF RADIO COMMUNICATION.

APPLICATION FILED EQJI, 191.2.

1,400,847, Patented Dec. 20, 1921.

Inventor:

ET T'ISt F. W. 6] lexanclerson,

b fly, 46%

His Jqttorneg.

ERNST r; w. mmmson, or scmnc'ranx; NEW YORK, A

' I mnc'rnrc comm, A conronarron or NEW appllcation'fled December 81,1918. Serial 1T0. 269,085.

imi'rrsu' smes;:P'AT M orifice.

SSIGNOR r0 GENERAL YORK.

' SYSTEM OF 'RADIO COMMUNICATIOI L To all whom it may concern:

. Be it known that I, 'ERNST F. W. ALEX- ANDERSON, a citizen of the United States;-residing at Schenectady, in the county of Schenectady, State of New York, have 1n-. vented certain new and useful Improvements in Systems of Radio Communication, of which the following is a specification.

My present application is a continuation in part of in prior application, Serial No. 49,422, filed eptember 8, 1915.

My invention relates to systems of radio communication having a hi h frequency alternator as the source 0 radio energy. While my invention in its complete aspect particularly relates to systems of radio communication c'ertain features of the invention are applicable generally to systems for the production of high frequency alternating current of approximately constant frequency. Broadly, the obj ect of my invention is to provide an improved continuous wave system of radio communication inwhich the source of radio'energvis of approximately constant frequency. More particularly the object of my invention is to provide a novel and improved speed regulating mechanism for a high frequency alternator employed as the source-of high.frequency ener 1n 3.

systemof radio communication. In its more general aspect, 'my invention has for one of its objects the provision of improved means for regulating the speed of a high frequency alternator for generating high frequency a1 ternating current of substantially constantfrequency Other objects of my invention, will bebrought out in the course of the fol;

; l wing description.

'Ktathe present time, there are two systems. of "radio communication, the so-called damped'wave system'which is the system commonly used at the present day, and the continuous wave system, which now promises to become the predominating feature in long distance .systems of communication. Aside from the fact that the-principle of wave motion is the same for both the, damped and the continuous wave systems, the apparatus for sending, as well as for receiving, is fundamentally different in the two systems, A continuous wave sending station consists of a source of high frequency alternating current energy which is delivered directly to the antenna. The simplest form of the continuous wave system is an Specification of Letters Patent.

is generated in the sult-ing superimposed upon the receiving circuit, a beat-frequency of 1,000 cycles is created. While radio-frequencies are entirel inaudible, the beat-frequency of 1,000 cyc es is one to which the human ear is'most sensitive. The heterodyne receiver has an absolute-select vity for signals within the range of Patented Dec. 20, 1921.

receiving station and about 5,000 cycles, which in practical com- 'f. mercial operation is the limit of audibility of the human ear. The beat-frequency,-'refrom the interference of the incoming signal waves of radio-frequency and the locally produced alternating current 'of slightly different frequency, iscaused to produce a musical note by-which the radio-signal is distinguished.

Since the signal in the heterodyne receiving system is distinguished by concentration of mind, on the part of the operator, on the sound of a certain musical note, and since 'fethe operator must distinguish this signal among a variety of other sounds, it is im-' portant that the sound of the receiving signal should be of practically constant pitch. The frequency of the sound wave for which the human ear ismost sensitive is between 500 and 1,000 cycles per second, and in the heterodyne receiver it is desirable that the frequency of the effective sound wave should not vary more than about 25 cycles, per second. If the frequency of the radio current is 25,000 cycles, this would mean a variation of 0.1 per cent; and if the frequency of the radio current is 50,000 cycles, the permissible variation would be 0.05 per cent. Where the radio current is derived from a high frequency alternator, it will be evident that a particularly uniform speed of the rotating member of the alternator is necessary. In fact, the requirements for constancy in speed regulation of regulators used with high frequency alternators in continuous wave systems of radio communication with heterodyne receivers are more severe than in any other electrical apparatus or system with which I am acquainted.

My present invention has for, one of its objects to maintain at a predetermined value the speed of a high frequency. alternator driven by a prime-mover deriving its power from an electric circuit. The invention is based upon the principle of sharp resonance in an auxiliary circuit acting, for example, upon the field of an electric motor driving the alternator, upon the field of an electric generator supplying energy to the motor or upon the circuit which supplies currentyto the driving motor. In accordance with my invention the current in the resonant circuit is rectified, and the rectified current acts directly, or through some amplifying means, upon the agencywhich is to be controlled.

The problem of providing any automatic mechanism intended for maintaining constancy of some quantity, like speed or voltage, is att'ended with considerable difiiculties. The principal diiiiculty lies in controlling the inertia of the various functions that take part in the regulation, such as the inertia of the waterin the pipe line of a turbine regulator, or the magnetic inertia in the field of a dynamo electric machine. Unless special precautions are taken to control this inertia, the regulator .does not work properly, or, as it. is termed, is apt to hunt, and consequently a variety of methods and means have been worked out depending upon the practicalconditions surrounding each problem of regulation. As for instance may be mentioned shunt-flow in the water wheel regulator, and the floating contact and anti-hunting contact in the Tirrill voltage regulator; In each of these cases, advantage is taken of the fact that the changes in load are usually slow, relative to the action of the parts of the regulator, and it is permissible to slow down the action of the regulator so as to allow it to gradually adjust itself ,to-

- the new condition, thereby avoiding overregulation and consequent hunting.

In providing a speed regulator for a radio-frequency alternator, the problem is made additionally difiicult, not only on account of the very exacting requirement of constancy, but on account of the-fact that the whole power-flow is changed at a very rapid rat during the sending of telegraph signals. Any method of avoiding hunting by slowing down the action of the regulator would not, therefore, be acceptable.

My present invention consists in providing a regulator mechanism which has therequired high accuracy and quickness of ac tion by introducing devices which so greatly magnify the indications of change of speed that these devices will in effect anticipate and reverse the action of the regulator parts high frequency alternator,

has carried it beyond the permissible limit.

More specifically, my present invention comprises the use of a highly tuned electric circuit energized by a current derived from the to be regulated, together with a rectifier associated with the tuned circuit and delivering rectified current to a relay for controlling the rest of the regulating mechanism. In addition,

I preferably employ means for l further amplifying the variations in energy,

which act upon the movable part of the regulator relay, after such variations in energy have been transferred from the tuned or oscillating circuit to the rectified circuit and thence to the winding of the relay. The means for amplifying the variations of energy acting upon the regulator relay preferably operate upon the differential principle where a variable force is opposed by a constant force, so that the resulting force has a greater percentage of variation than V the original variable arrangements that may expediently be used force. The differentialv include the opposition of a constant electromotive force against the rectified electromotive force,the opposition ofthe tension of v a spring against the force of the magnet in the regulator relay,-the opposition of a permanent magnetic field in the relay against the field superimposed by the magnetism of the relay, or the use of the differential action between the radio frequency and a slightly different frequency in a manner analogous to the heterodyne receiver. All of these methods for amplifying the variations of energy acting upon the relay may be used in combination, or-any one may be used alone. Those'skilled inthe art will and their combinations may also be devised for accomplishin the same purpose.

The system which I have chosen to illus' trate the principle of my invention comprises a high to the motor.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, as to its organization and method of operation, to-

as I

its recognize that many other equivalent ,means 11'0 frequency alternator driven byv three-phase electric motor supplied with' electric energy from a distribution system.

. whose speed is in the shape of a disk designed for maximum strength and having a plurality of gether with further objects and advantages thereof, will best be understood by reference to the following description taken in connection with the accompan ing drawing in which I have illustrated iagrammatically one way in ich my invention may be carried into efi'ect.

. "The system illustrated in the accompanying drawing comprises the usual antenna 1 with the tuning inductance 2; The antenna is connected to the armature winding of a radio frequency alternator 3 through a radio.

transformer havin a secondary'winding 4.

' The armature of t e alternator 3has a plurality ofcoils 5 independently connected to a plurality of primary coils 6 supplying cur rent to the secondary 4 of the transformer.

tenna' 1 and has one terminal connected to ground in the well known manner. The radionfre'quency alternator, which I have dia grammatical y represented in the drawing, is of the inductor type described in my U. S. Letters Patent No. 1,008,577, November 14, 1911, No. 1,110,029, September 8, 1914, and

No. 1,110,030, September 8, 1914., The alternatorhas a stationary laminated iron armature member carrying the coils 5 'and has a rotatably mounted rotor or inductor member slots for lpxro'ducing magnetic poles therebeuration regulator which comprisesmagnetic tween. is represented in the drawing at '7 and is mounted on a rotatable shaft 8. A threephase alternating current motor 9 is also coupled to the shaft 8 and operates to drive the inductor 7 of the alternator. The motor 9 receives power from thesupply conductors 10. The current supplied to the motor is" controlled by a variable impedance or satcores 11 with windings 12 thereon, which carry the current su ply to the motor, and with additional wind1ngs'13which carry the saturating current of the cores 11,.whichis used for controlling the current supply to v the motor. The operation of this regulator will be described more in detail later.

1 The flow of power from 'the high fre queney alternator to the antenna, and hence the energy radiated from'the antenna, is controlled by a magnetic controller or amplifier. This magnetic amplifier is of the type described in the Letters Patent of the United States of James C. Armor, No.

' 1,219,215,'while the particular form of the vember 26, 1915, and Serial No. 227,946,filed April 11, 1918.

In the circuit connection here illustrated from the antenna. and off the alternator by operation of the e inductor rotor of the alternator fa. battery 16. The reactive windings 14 are connected in shunt to the secondary winding of the transformer-4. -A telegraph key 17v controls the flow'of currentin the winding 15. When the telegraph key 17 is in the position shown in the drawings the controlling winding 15' is ener ized and the impedance of the reactive windings 14 is a minimum so that the secondary winding 4 is substantially short-circuited and little or no energy is radiated-from the antenna 1. When it is desired to send a signal, telegraph key 17 is depressed, thereby opening the circuit of the controlling winding 15, whereupon the impedance of the reactive windings 14 is raised to its maximum value and energy is radiated Power is thus taken on telegraph'key.

The speed regulator for the alternator should act in such a way that the power of the motor 9 is changed with the telegraph signals so that the torque-of the motor is varied an amount corresponding to the load on the alternator before an appreciable change in speed of the generating unit has taken place.

The current-supplied to the motor 9may .be varied by varying the magnetic saturation of the cores 11, and hence varying the impedance of the windings 12, which are in series with the source of supply. The current supply for saturating the cores 11 is obtained from a direct current generator 18. The approximate adjustment of the torque of the motor 9 may be obtained by means of a resistance 19 which is included in the circuit which supplies current from the enerator 18 to the saturation coils 13. his resistance is controlled b the manipulation of-the telegraph: key. hen the telegraph key is depressed to send a si al theresistance 19 is short-circuited by t e engagement of the key with the fixed contact 20. The current in the saturation current coils 14 is thereby increased and the current supplied to the motor and hence the torque of the motor, is increased to approximately c0rrespond to the change in the load on the alternator,

The tuned circuit of the automatic s ed regulating mechanism is fed from one o the in ependent-armature circuits of the alternator, and the voltage supplied thereto "is thereby rendered independent of the load on the machine. This circuit includes an ad'- justable inductance 21 for tuning purposes, a condenser 22 and the primary 23 of a transformer. The secondary 24 ofthis transformer is included in the rectifier circuit which also includes. the rectifier 25 and the winding 26 of therelay 27. In the present case a mercury vapor rectifier is shown but this is not essential as other forms of rectifier may be used if. desired. The regulator can be adjusted for different speeds and corresponding frequencies by changin the inchanging the capacity of the circuit or by,

changing both capacity and "inductance.

- Variations in the adjustment may also be ac-l complished if desired by varying the con.-

' 'pling enw to'the rectifier circuit.

I y en. a mercury vapor rectifier is used in a re ating mechanism embodying my invention, the counterelectromotive force of a few volts of the rectifier provides a differ: ential means for emphasizing or accentuat: ing the variations in the rectified current hereinbefore mentioned. The voltage necessary for maintaining the rectifier continu- 1 ously in an operating condition is supplied ,by a directcurrent enerator 28 which is ;-";-"connected to the recti' er in the well known manner; r With the arrangement which I have shown the rectified voltage supplied from the alternator must exceed the counter electromotive force of the rectifier before anycurrent will flow inthe rectified circuit. The current flowing in the. winding 26 is thus determined by the difi'erence bet-ween the rectified voltage and the counter electromotive force due to the rectifier and a change in the rectified voltage thus produces a greater percentage change in the relay current than would be the case if the differential action of a counter electromotiveforce were not employed. In this way a particular change in the rectified voltage becomes moreefi'ective, or in other words, is accentuated or emphasized. It will of: course be apparent that any other rectifier which has a counter electromotive force will produce the sameeffect The relay 27.has a movable element or armature 29, which opens and closes a contact 30. When the armature 29-is in the position indicated, the winding 31 of a second relay 32 is short-circuited. ,When, howcontact 30 this short-circuit is removed and current from the direct current generator 28 is supplied to the winding 31 to operate the,.,-relay 32. The opening and closing of ct'33 of the relay 32 serves to open and tliii circuit of the field winding 34 of enerator 18, which supplies current to the saturation coils 13. Thus whenever the magnetizingfaction ofthe relay 27, due to the current flowing in its winding 26 is sufgenerator ductance of the coil 21 in the tune circuit..- This change can obviously also be made by plied to winding 35 is mature 29. s at once pulled up by spring between the primary 23 and the sec-, ondary 24 of the transformer which supplies .maintaining a pulsating voltageon the gen xrent supplied to the slowing down the alternator.

ever, the armature 29 operates toopen the,

ficientlygreat to attract the armature 26 the field winding 34: of the generator 18 is opened and the saturation current supplied; to the coils 13 is interrupted. The relay, 27 is provided in additionto the winding 26 with a second winding 35 which is supplied with current from the 18. This windingis so arranged as to assist the winding 26 inattracting the. armature in opposition to the pull of spring ".75- 36.- When the armature 29 isattracted so as to open contact 30- and'the field 340i generator 18 is thus opened, the current supreduced and the ar- 36. to reestablish the contact 30. As a result of this action the contacts-30 and 33 are caused to vibrate at a high rate of speed,

erator18.

The resonant circuit which supplies current to the rectifier 25 is preferably adjusted for a frequency slightly higher than that at which the alternator is intended to operspeed of the alternator will produce a large increase in the current in the rectifier circuit sup lied to the winding 26 of relay 27. This w1l cause the relay 27 to operate somewhat sooner than itwould with the normal current in the rectifier circuit, and consequently the field circuit of generator 18 will be opened sooner and remain open for a longer interval-than under normal conditions. .As a result less current will be supplied to the saturation coils 13 and the curmotor 9 will decrease,

The operation of the regulating system will be improved by the use of a condenser 37- in shunt to the secondary 24 of the trans former by which current is supplied to the rectifier. Since the current in the rectifier circuit is a high frequency pulsating current a condenser 38 is preferably inserted in shunt to the winding 26 in order to smooth out the pulsations in the current supplied to that winding. When the coils 12 of the saturation regulator are connected, as shown, they'form a low resistance secondary for the saturation coils 13 in order to pernut-the current in the saturation coils 13 to quickly build up to its maximum value, it. is therefore desirable to provide resistances 39 in series with the coils 12. The rheostat 40 is provided for adjusting the saturation current supplied to the coils 13 when the key 17 is depressed. The rheostat 41 admits the adjustment of the current supplied to the winding 35 and the rheo'stat 42 is provided for adjusting the current in the field "34 of generator 18.

It will be evident from the foregoing description that the speed regulating mechanism involved in my invention is extremely tion t ereto. The regulator relay will thus reverse the action of the means controlling the power flow to the alternator shaft before sufficient inertia has been given to the controlling function to make the power flow over travel more than the amount corresponding to a change in radio frequency that would give a low note in a telephone. The flow of energy to the alternator shaft is therefore so controlled that the difference between the maximum and minimum frequencies of the alternator corresponds to a frequency not higher than one which would produce a lowv note in a telephone.

While I have described a single embodiment of my invention, it will be apparent to one skilled in the art that my invention 1 is not limited to the precise arrangement shown but that many modifications may be made in the circuit. arrangements and apparatus usedwithout departing from the scope of my invention as set forth in the appended claims.

. What I claim as new and desire to secure by Letters Patent of the United States, is

tric circuit electrically associated with said auxiliary electric circuit, means whereby the current-flow in said rectifying circuit has a greater rate of variation than the currentflow in said auxiliary circuit, and means responsive to variations in the current-flow in said rectifying circuit for varying the speed of said alternator.

2. A system for the production of high frequency alternating current of substantially constant frequency comprising in combination a high frequency 'alternator, an auxiliary electric circuit sensitive to variations in frequency electrically associated with said alternator, electric current rectifyin means associatedwith said auxiliary circuit, and means responsive to the rectified current resulting from the action of said last mentioned means for controlling the speed of said alternator.

3. A system for the production of high frequency alternating current of substantially constant frequency comprising in combination a high frequency alternator having a plurality of independent armature circuits, a source of power for driving said alternator, means for deriving from one of the armature circuits of said alternator a unidirectional electric current varying as a function of the frequency of the current generated by the alternator, and means responsivetochanges in the value of said unidirectional current for varying the application of power from said source to said alternator.

4. A system for the production of high frequency alternating current of substantially constant frequency comprising in combination a high frequency alternator, a

source of power for driving saidalternator,

an electric circuit associated with said alternator and adapted to receive a current of the frequency generated by the alternator, means for tuning said circuit for a frequency slightly different than the frequency of the alternator current, means for producing a unidirectional electric current correspondingto the alternating current flowing in said electric circuit, and means responsive to changes in the value of said unidirectional current for varying the application of power from said source to said alternator.

5. A system for the production of, high frequency alternating current of substantially constant frequency comprising in combination a high frequency alternator having a plurality of independent armature -cir-. cuits, a source of-power for driving said alternator, a tuned electric circuit associated with said alternator and adapted to receive from one of said armature circuits a current of the frequency generated by the alternator, means for producing a unidirectional electric current corresponding to the current flowing insaid tuned cicuit, and electromagnetic means responsive to changes in the value of said unidirectional current for varying the application of power from said source to said alternator.

6. A system for the production of high frequency alternating current of substantially constant frequency comprising in combination a high frequency alternator, a source of power for driving said alternator, a tuned electric circuit associated with said alternator and adapted to receive a current of the frequency generated by the alternator, means for producing a unidirectional electric current corresponding to the current flowing in said tuned circuit, means for emphasizing the variations in said unidirectional current, and means responsive to the emphasized variations in said unidirectional current for varying the application of power from said source to said alternator.

7 A system for the production of high frequency alternating current of substantially constant frequency comprising in combination a 'high frequency' alternator, a prime-mover for driving said alternator, a tuned electric circuit associated with said alternator and adapted to receive a current of the frequency generated by the alternator, a second electric circuit electrically associated with said tuned circuit, an electric current rectifying device in said second circuit, a relay responsive tochanges in the current flowing in said second electric circuit, and means controlled by said relay for varying the speed of said prime-mover.

I 8. .A system of electrical distribution comprising in combination a high frequency alternator, an auxiliary electric circuit sensitive to variations in frequency electrically associated with said alternator, a current rectifying electric circuit electrically associated with said auxiliary circuit, and hav: ing an approximately constant counter-electromotive force which opposes the flow of current in said rectifyingcir'cuit, and a re-' lay included in said rectifying circuit and adapted to vary the speed of said alternator.

9. A system of electrical distribution'comprising in combination a high frequency alternator, an auxiliary electric circuit sensitive to variations infrequency electrically associated with said alternator, electric current rectifying means associated with said auxiliary circuit, a relay having a movable armature responsive to the rectified current resulting from the action of said last mentioned means, means whereby the force actuating the movable armature of said relay varies at a greater rate than the square of the current in the auxiliary circuit sensitive to frequency variations, and means controlled by the movable armature of said relay for varying the speed of said alternator. g

5 10. A system of electrical distribution comprising in combination a high frequency alternator, means for supplying energy to the shaft of said alternator, an auxiliary electric circuit sensitive to variations in frequency electrically associated with said alternator, electric current rectifying means associated with said auxiliary circuit, a relay responsive to the rectified current resulting from the action of said last mentioned means, means controlled by said relay for varying the speed of said alternator, and means for emphasizing the effect of said rectified current.

11. A system of electrical distribution comprising in combination a high frequency alternator, an auxiliary electric circuit sensitive to variations in frequency electrically associated with said alternator, electric current rectifying means associated with said auxiliary circuit, a relay responsive to the rectified current resulting from the action of said last'mentioned means and adapted to an alternating current generator, a source of power for driving said generator, means for deriving from said generator a unidirectional electric current which varies as a function of the frequency of the current generated thereby, and means responsive to changes in the value of said unidirectional current for varying the application of power from said source to said generator.

13. A speed regulating system comprising an alternating current generator, a source of power for driving said generator, a tuned electric circuit associated with said generator and adapted to receive a current of the frequency generated, means for producing a unidirectional electric current corresponding to the current flowing in said tuned circuit, and electromagnetic means responsive td-changes in the value of said unidirectional current for varying the application of power from said source to said generator.

14. A system for the production of high frequency alternating current of substantially constant frequency comprising in combination a high frequency alternator, anelectric motor for driving said alternator, a timed electric circuit associated with said alternator and adapted to receive a current of the frequency generated by the alternator, -a second electric circuit electrically associated with said tuned circuit, an electric current rectifying device in said second circuit, a relay responsive to changes in the current flowing in said second electric circuit, and means controlled by said relay for varying the current supplied to said motor.

15. A system for the production of high frequency alternating current of substantially constant frequency comprising in combination a high frequency alternator, an alternating current motor for driving said alternator, a tuned electric circuit associated with said alternator and adapted to receive a current of the frequency generated by the alternator, a second electric circuit electri cally associated with said tuned circuit, a relay responsive to changes in the current flowing in said second electric circuit, a supply circuit for supplying current to said motor, a variable impedance in said supply circuit, and means controlled by said relay for varying the value of said impedance.

16. A system for the production of high frequency alternating current of substantially constant frequency comprising in combination a high frequency alternator having a plurality of independent armature coils, a prime-mover for driving said alternator, a tuned electric circuit associated with one of an alternatingcurrent generator, an electric motor for driving said generator, a source of current for controlling the speed of said motor, means for deriving from said generator a unidirectional electric current which varies as a function of the frequency of the current generated thereby, and means responsive to changes in the value of said unidirectional current for controlling the voltage of said source of current and thereby controlling the speed of said motor.

18. A speed regulating system comprising an alternating current generator, an electric motor fdr driving said generator, a source of current for controlling the speed of said motor, means for deriving from said generator a unidirectional electric current which varies as a function of the frequency of the current generated thereby, and means responsive to changes in the value of. said unidirection current and to the voltage of said current source for varying the current supplied from said source, and thereby controlling the speed of said motor.

19. A speed regulating system comprising an alternating current generator, an electric motor for driving said generator, a source of current for controlling the speed of said motor, means for deriving from said generator a unidirectional electric current which varies as a function of the frequency of the current generated thereby, an electromagnetic means responsive to changes in the value of said unidirectional current and of the voltage of said source of current for varying the current supplied by said source, and thereby controlling the speed of said motor. v

20. A; system for the production of high frequency alternating current of substantially constant frequencycomprising in combination a highv frequency alternator, an electric motor for driving said alternator, a source of current for controlling the speed of said motor, means for deriving from said alternator a unidirectional current which varies as a function of the frequency of the current generated thereby, and a relay responsive to changes in the value of said unidirectional current and the voltage of said source of current, for controlling the current supplied from said source, and thereby controllin the speed of said motor.

21. system for the production of high frequency alternating current of substantial y constant frequency comprising in combination a high frequency alternator having a plurality of independent armature circuits, an auxiliary electric circuit sensitive to variations in vfrequency electrically associated with one of the armature circuits of said alternator, electric current rectifying means associated with said auxiliary circuit, and

means responsive to the rectified current re-.

sulting from the action of said last mentioned means for controlling the speed of Said alternator.

In witness whereof, I have hereunto set my hand this 30th da of December, 1918.

ERNST F. W. LEXANDERSON. 

